Uptake of 15N by Macrophytes in Subsurface-Flow Wetlands Treating Domestic Wastewater

• Published in: Environmental technology Vol. 22; no. 7; pp. 837 - 843
• Main Authors: Weaver, R. W., Lane, J. J., Johns, M. J., Lesikar, B. J.
• Format: Journal Article
• Language: English
• Published: London Taylor & Francis Group 01.07.2001; Selper
• Subjects: ammonium; Applied sciences; Biological and medical sciences; Biological treatment of waters; Biotechnology; Constructed wetlands; Ecosystem; Environment and pollution; Eutrophication; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Industrial applications and implications. Economical aspects; macrophytes; Nitrogen - metabolism; Nitrogen - pharmacokinetics; Nitrogen Isotopes - pharmacokinetics; Other wastewaters; Plants; Pollution; secondary effluent; Waste Disposal, Fluid; Wastewaters; Water Movements; water quality; Water treatment and pollution; Domestic waste water; Nitrogen 15; Artificial medium; Aquatic plant; Waste water purification; Wetland; Subsurface; Biological purification
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/095933322086180316

Constructed subsurface-flow wetlands are becoming more common for on-site treatment of domestic wastewater to provide secondary quality effluent. Macrophytes are generally added to wetlands to increase treatment efficiency but their role in reducing N content is controversial. Our investigation utilized two subsurface-flow wetlands to determine the efficiency of different macrophytes in uptake of 15N labeled ammonium sulfate. Macrophytes in Wetland 1 recovered 35 % of the added N in their shoots but only 5 % of the added N was recovered in the shoots and roots in Wetland 2. A major difference for the two wetlands was N and hydraulic loadings. Wetland 1 received 7.5 Kg N ha-1d-1 and Wetland 2 received 16.9 Kg N ha-1d-1. Retention time for Wetland 1 based on pore volumes was 2.9 d and for Wetland 2 it was 1.2 d. The retardation factor for NH4+ was approximately 2.5 for both wetlands and the breakthrough curves indicated lack of plug flow. The importance of macrophytes in taking up NH4 appeared to dependent on N and hydraulic loadings.